Memcpy precise buffer size in seg_mask
Memcpy precise buffer size in seg_mask

Use precise buffer size to copy the seg_mask in handle_inter_mode().
Tested on bus_cif at 30 frames 1000 kbps, it improves the encoding
speed by 2.3% at spee 1. Overall runtime 1542s -> 1459s.

Change-Id: Ibe730effee1e370d6a5236eaffdf13c37aae6893

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom